The objectives of this project are to study the interaction of PTH and adenylate cyclase from osseous tissue, exploit this knowledge for the standardization of a sensitive PTH bioassay and examine the effect of PTH on cell proliferation in the context of cAMP changes. Adenylate cyclase experiments will be carried out on partially purified plasma membranes from embryonic rat calvaria and rat osteosarcoma. Cell cultures derived from these tissues will be used for the study of PTH effects on proliferation. Separate clones of cAMP-PTH-responsive and non-responsive osteosarcoma cell lines, recently established in our laboratory, will help elucidate the role of cAMP in PTH action.